brisket temperature

First time to ever use smoker. Ok so I jumped the gun and purchased an 18 pound brisket ( instead of an 11 pounder). I cut in in half and placed both pieces in the smoker at 200 degrees. It has now been 16 hours and the internal meat temperature is only 170 degrees. Why cant I get to 190 degree internal meat temperature? Is it because of the extra pounds. Even the smaller piece of brisket is not at the desired 195 temperature?